A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air entering the compressor section is compressed and delivered into the combustor section where fuel is injected into the air flow. The combustion of the fuel with the air passing though the combustion section generates a high temperature gas flow which upon expansion through the turbines produces the shaft power required to drive the compressor and the fan section. The compressor section typically includes low and high pressure compressors, and the turbine section includes low and high pressure turbines.
An airflow path between rotating blades and fixed vanes is defined by inner and outer shroud structures. The shroud structures are attached to corresponding housings to define a gas flow path. Axial gaps between the fixed shroud structures and rotating components are required to accommodate axial shifting and expansion during operation. However, the size of the gaps is minimized to reduce airflow losses that reduce engine efficiencies. Radial Assembly of the inner diameter shrouds includes moving the shroud portions from a radially outer position past rotating and other fixed components into the desired assembled position. Size and component locations can prevent axial movement of a shroud during assembly, thereby limiting assembly to only radial movement. In such cases Radially outer structures of rotating or fixed components can interfere with the radial assembly of the case containing the inner shroud structures if the inner shroud structures are sized axially to minimize the axial gap between the inner shroud and the adjacent components when they are in the assembled position. One solution to this problem is to reduce the axial extent of the inner shroud structure so that it would clear the radially outer structures during radial assembly but this would be unacceptable if the resulting axial gap between the inner shroud structure and adjacent component(s) (typically a rotor) becomes larger than that required for efficient interference-free operation of the machine.
Turbine engine manufacturers continue to seek further improvements to engine performance including improvements to assembly, heat transfer, and thermal and propulsive efficiencies.